


Similarities

by maiselocked



Category: Criminal Minds (US TV), Sherlock (TV)
Genre: Brother-Sister Relationships, Chaptered, Crossover, F/M, Mycroft Being Mycroft, Protective Older Brothers, Reader-Insert, Sherlock Being Sherlock, Spencer Reid Fluff, sherlock's twin sister
Language: English
Status: In-Progress
Published: 2021-01-07
Updated: 2021-01-15
Packaged: 2021-03-17 15:40:34
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,583
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28602342
Author URL: https://archiveofourown.org/users/maiselocked/pseuds/maiselocked
Summary: Spencer Reid frequently wondered if there were soulmates, if there was someone out there that was made just for him, who's hand would fit perfectly into his, who would understand his feelings, who would listen to him and love him unconditionally. He almost gave up. He thought he was delusional.And then a sliver of hope came in the form of the Holmes siblings walking into the Behavioral Analysis Unit's office in Quantico. Sherlock Holmes and his arrogant stares, Mycroft Holmes with his nose turned up ever so slightly, and Y/N Holmes with mismatched earrings and a book almost falling out of her bag.
Relationships: Spencer Reid/Reader
Comments: 9
Kudos: 90





	1. it was a peaceful day

**Author's Note:**

> hi! so this is a rewrite and continuation of similarities, a story i had posted a few months ago. looking back at it, i love the concept and the story but hated the way i wrote it so i'm gonna restart it and finish it here! 
> 
> this is a sherlock and criminal minds crossover. y/n is sherlock's twin but let it be known that they aren't identical but if you are reading, you can imagine it however you like. i hope you enjoy!

It was supposed to be a quiet day off. Let that be known from the beginning. The past case Sherlock had taken on resulted in a broken rib here and there, an almost broken nose, sore feet from running all across London, and the need to sleep for 15 hours. You were so close to receiving those 15 hours but then Sherlock was yelling and Mycroft was coming up the stairs with his umbrella clicking on the creaky wood and you had to wake up after 13 hours of sleep. 

“Where is Y/N?” asked Mycroft from the front door. Sherlock was laying down, hands steepled under his chin. 

“Coming down the stairs,” he answered quickly. True to his word, you shuffled down the stairs with a stifled yawn. “Good afternoon.” 

You waved your hand in a greeting before yawning again. “Hey.” 

“Good afternoon, sister,” said Mycroft. He waited until you took a seat in your respective lounge chair pushed between John and Sherlock’s before speaking again. “We’re flying to Quantico.” 

No more than a second after those words come out of your older brother’s mouth did you automatically refuse. “No! No. I just chased around a serial killer for two weeks and I’m exhausted.”

“You haven’t heard why,” Mycroft interjected. 

“I don’t care-” 

“Why, Mycroft?” Sherlock asked. 

You rolled your eyes but listened nonetheless. “For the past month, several victims have turned up around the U.S. and we have reason to believe it’s the same serial killer from six months ago that attacked upwards of 15 people. I’m sure you both remember the case.” You nodded your head in remembrance of the one time you completely avoided Sherlock out of fear he’d start convicting you of the murders. “The FBI has taken on the case, particularly their Behavioral Analysis Unit. I believe our assistance could benefit them. I would send you two alone but I don’t trust you so I’ll be going as well.” 

“Hey! I’m responsible, thank you very much,” you shouted in defense of yourself. 

“No. You’re passive. Responsible, maybe, but you tend to let people walk over you. I could do almost anything I wanted to and you wouldn’t stop me,” Sherlock rambled out quickly. 

“Stop psychoanalyzing me! I am not a pushover. I should’ve absorbed you in the womb when I had the chance.” 

“Oh please, I would’ve absorbed you way before you would even have the chance.” 

Mycroft hit his umbrella against the wall. “Shut up. Both of you. Do you understand now why the older brother has to tag along?” You grumbled out a yes. “Good. The jet leaves in two hours. Pack accordingly. It’s currently 35 degrees in Virginia.” 

With that, Mycroft left 221B and got into the sleek black car that drove him home. Reluctantly, you got up and headed to the kitchen to make some tea before trying to pack. Sherlock stayed on the couch until he heard the familiar clinking of tea cups. “Two sugars.” 

“Who said I was making tea for you?” 

“I’ll call mother.” 

“You won’t.” 

Sherlock picked up his phone. “I will.” 

“Fine!” 

-

“You’re not late,” Mycroft announced as Sherlock and yourself stepped out of the black town car he had sent 30 minutes earlier. The driver heaved your suitcases out of the trunk and handed them to a worker at the airport where Mycroft had called in a jet. How he managed to secure a private jet in such a short amount of time, you didn’t know, but nevertheless you got on. 

“So, just for clarification, we’re flying all the way to Virginia to assist the FBI in a case that we’re not even 100% positive is the same one from 5 months ago?” You asked almost incredulously. 

Mycroft nodded. “I’m positive.” 

“And have the FBI asked for our help?” 

Mycroft shook his head. 

“Wonderful.” 

Within 30 minutes, the jet took off and you were already dozing off. Sherlock and Mycroft remained respectfully quiet, whispering when either had something to say. It almost made you smile. Just almost. 

It was an unconventional family, that was for damn sure. How your parents managed to have three kids with brains so unimaginably complex was beyond you and Mycroft and Sherlock rarely outwardly showed their love but you had learned to see it in their small actions. Sherlock was a prat but he made your tea perfectly, never used your personal blanket, put himself in between you and danger when in a case. Mycroft watched you through security cameras when he was worried, he offered up his guest bedroom plenty of times when Sherlock was shooting at the wall, and he listened. 

The flight to Quantico was reasonably long, ranking in at 9 hours and passing through multiple time zones. You woke up feeling somehow more tired than before and begged Mycroft to allow you to stay in a hotel just for the rest of the day and night and visit the FBI in the morning. He reluctantly allowed, putting the three of you up in a 5-star hotel in D.C. 

“Y/N! Are you awake?” Sherlock asked from the foot of your bed at 7 in the morning. 

“Leave me alone. Let me sleep more,” you grumbled. In an attempt to block out the harsh light coming from the room, you pulled the blankets over your head. Suddenly though, cold air hit the entirety of your body as Sherlock pulled the blankets away. “What the hell?!” 

“We’re leaving at 8.” 

“Fine, I’m up.” 

“Pushover.” Quickly, you threw a pillow at his backside when he walked away which he returned with a dramatic slam to your door. 

The following hour was spent dragging yourself through your hotel room, trying on different combinations of outfits, styling your hair different ways, wishing that a cup of coffee would magically appear on the counter. By 7:56, you slung your bag over your shoulder and stepped out of your hotel room. 

Mycroft and Sherlock were already standing, having been awake for hours (you didn’t know how they did it quite honestly), and then the three of you made your way downstairs where a car was waiting to transport you to the FBI headquarters.   
The ride was relatively silent. Mycroft spent it combing through files, Sherlock typing rapidly on his phone, and yourself staring out the window with a few glances here and there to the book in your lap. An argument about your attention span almost broke out between yourself and Sherlock but Mycroft stepped in beforehand, which the driver greatly appreciated. 

It wasn’t long before the car took a spot in the parking lot and the three of you stepped out. Mycroft pulled out two ID cards from the inside of jacket pocket and handed them to you and Sherlock. “You’re members of the SIS for now. Don’t think this will get you anywhere, Sherlock. They’ll be deemed inactive the minute you step foot in London. They’re precautionary measures.” 

“I don’t need this,” Sherlock said while putting the badge inside of his coat. You clipped yours to the pocket of your jacket and followed your brothers into the FBI building. 

Mycroft spoke with a receptionist and some other agents before he signaled for the two of you to follow him towards an elevator where he pressed the button for the 5th floor. “The Unit Chief is named Aaron Hotchner. There are 6 members and a technical analyst they work with,” Mycroft said while typing on his phone. 

The elevator dinged and the doors opened. Mycroft led with Sherlock next to him while you lingered just a few steps behind due to the significant difference in height. The bullpen was empty, as was the office of the Unit Chief and Mycroft was the first to notice that they were all seated in the briefing room across the floor. 

“Morgan and Prentiss, I want you to visit the most recent victim’s home and find what you can there. Rossi and I will-” 

8 heads turned when the door to the briefing room opened. Mycroft stepped through, followed by Sherlock, and then you. 

The group in front of you stared at each other awkwardly. “Who are you?” asked the man standing in front of a large screen with graphic images on it. 

“Mycroft Holmes. This is my brother Sherlock and my sister Y/N Holmes.” 

“And what are you doing here?” 

“We’re here to help you solve the case.”


	2. that insufferable detective

“Again, who are you?” The man at the front asked again.

Mycroft was about to respond hastily but you stepped in front of him, deciding to put everyone out of their misery. “Please excuse my brother. He severely lacks communication skills. Sherlock and I worked on a case a few months ago and Mycroft has reason to believe it’s the same case as the one you’re working on currently.” 

“Wait,” came a woman a few seats away from you. “Holmes. Sherlock Holmes. You’re that insufferable detective who works in the Scotland Yard.” 

Sherlock scoffed. “I would never work in the Scotland Yard. I’m a consulting detective. I solve cases when people are too incompotent to solve them themselves.” 

“We solve cases, thank you very much,” you added. “Look, if you don’t want our help, that’s fine, but Sherlock and I know this case inside and out. Mycroft is practically the entire British government, he just won’t admit it.” 

Only a few seconds after your spiel, you locked eyes with a man sitting on the opposite side of the table. He looked young, a lot younger than you’d expect an FBI agent to and was dressed in a cardigan and gray button up. Your cheeks turned hot under his gaze but you couldn’t bring yourself to look away and it seemed like he couldn’t either. 

“Is the whole crazy genius thing true? Like you can look at someone and tell them their whole life story?” the woman from earlier asked Sherlock. 

“Oh God,” you whispered. 

“Here we go,” replied Mycroft. 

“You’ve likely traveled a lot, spent some time in England considering your amount of knowledge about me and who I am. Word travels quickly. You’re determined to prove yourself in a male-dominated field which also makes me think your parents, specifically your mother, gave you a hard time as a child,” Sherlock rambled out quickly. “You own a cat that you cuddle quite frequently despite your assertion that you’re not affectionate. How lonely are you truly,” Sherlock picked up a file sitting in front of her, “SSA Emily Prentiss?” 

The agent blinked, her jaw stuck open. 

“What just happened?” asked one of the other unit members. 

“He just deduced her,” said the same man you locked eyes with. 

“Seduced her?!” 

“My brothers and I share a talent for deductions and observations. We’re able to draw accurate inferences from the smallest details that nobody else is looking for,” you explained. 

The man who was standing, who you assumed was Unit Chief Hotchner after observing him for a while, spoke again. “I suppose it wouldn’t hurt to have some extra help before this gets even worse. I’m Aaron Hotchner, these are agents Rossi, Jareau, Morgan, Prentiss, and Dr. Reid. This is our technical analyst, Penelope Garcia.” 

“Hey, do you think they’re smarter than pretty boy?” Morgan asked the blond woman, Agent Jareau, next to him. “What’s your IQs?” 

“IQ tests are hardly capable of measuring intelligence levels. Identifying complex shapes and patterns is a kindergarten level problem,” Sherlock complained. 

“He’s only saying that because we scored the same. 185. Y/N got a 188,” Mycroft answered. 

“She’s smarter than boy genius!” Penelope shouted. 

“Okay, can we begin now?” the Unit Chief asked. Everybody took a seat, Mycroft and Sherlock nominating to stand rather than to sit but you took the empty seat in between Dr. Reid and Agent Rossi. Rossi shook your hand in greeting and Dr. Reid awkwardly raised his hand before looking down with the tips of his ears growing red. 

-

Spencer was terrified. That was the simplest way to put it. She had mismatched earrings, her hair was pulled back into the messiest bun (if you could call it that) he had ever seen, and two overprotective brothers who no doubt noticed every time he even glanced her way. 

She was technically smarter than him by one point and he couldn’t be more intimidated. It certainly didn’t help that she was so incredibly close to him. Her accent was thick when she spoke, similar to her brothers. The similarities between her and the curly-haired Holmes sibling were uncanny and Spencer figured they were twins. Mycroft was obviously the oldest. 

Hotch was speaking intently with Mycroft while Y/N fiddled with her hands. She was nervous but he didn’t know why. She hid it well too. Nobody else noticed her fidgeting but Spencer always was observant. 

“So even the smartest siblings of England couldn’t catch this guy, huh?” Derek teased. Y/N scoffed out a laugh, responding to the simple joke a lot better than her brothers took it. 

“The alleged smartest FBI agents can’t catch him either so where does that leave us?” Mycroft retorted. 

Spencer watched Y/N sit up. “Can we not argue about who’s the smartest right now? This guy has over 10 bodies under his belt, possibly more, and he’s not stopping.”

“Y/N’s right,” Spencer added. “We don’t have a set profile but we know he’s not gonna stop. He’s getting some kind of high from this.” 

Y/N smiled at Spencer with a sort of appreciation or thankfulness for his words. 

Hotch began to discuss a plan of action for the rest of the day, altering it just enough to include Mycroft, Sherlock, and Y/N. “What do normally do during a case?” 

“Sherlock and I will visit the scenes,” Mycroft answered. “Y/N will visit the morgue and check the discovered bodies.” 

“You can go with Rossi and I to the scenes. Reid, do you mind taking Y/N down to the lab?” Hotch asked. 

Spencer froze, if just for a few seconds, like a deer in headlights. Alone time? With Y/N? Dear God, save him now. “Yeah, of course.” 

“Prentiss, Morgan, I want you to visit the family of the most recent victim. JJ and Garcia, you know your jobs,” Hotch said and with that, the group split off. 

Spencer didn’t even notice Y/N rise from her chair and begin to walk off. She turned and laughed at Spencer. “You coming or not, pretty boy?” She said, placing air quotation marks around his nickname. 

“Uh. y-yeah. Sorry! Coming.” 

The two walked out of the briefing room, Mycroft and Sherlock staring at their backs as they left. 

“He likes her,” Mycroft said. 

Sherlock smirked. “She likes him too.”


	3. i'm nothing special

Spencer jogged to match your pace and quickly fell into line beside you. His hand gripped onto his cardigan, knuckles almost turning white, and you took notice. 

“There’s no need to be nervous,” you said lightheartedly. “I’m nothing special.” 

“Technically speaking, you are. You’re incredibly intelligent and gifted with skills of deduction and observation. I’m sure you’re well educated too,” Spencer rambled before he could stop himself. He looked at you with trepidation and found you smiling. 

“The University of Edinburgh in Scotland. Doctorates in psychology and neuroscience. One bachelor’s in biology. Just couldn’t stop learning. You?” 

The ends of Spencer’s lips twitched up in somewhat of a smirk. “Doctorates in mathematics, chemistry, and engineering. Two bachelor’s in psychology and sociology.”

“I bestow the most-college-degrees crown onto you, good sir,” you said with a laugh and a dramatic bow. “Sherlock’s a graduated chemist but he does nothing with it except weird little experiments with body parts. Don’t think he’s a serial killer or anything though. He’s just friends with a girl at the morgue.” 

Spencer pressed the button for the elevator and with a soft ding, the doors opened and then closed when you stepped in. It was silent but not uncomfortably so and Spencer was eternally grateful for this. The quiet noise of your nails tapping against your phone screen filled the small room and once a quick message was sent to John (poor man had been left at home with Rosie), you pocketed the phone. 

“I wonder if Agents Rossi and Hotchner are ready to kill my brothers,” you thought out loud. 

“Why would they do such a thing?” asked Spencer innocently. 

You chuckled. “They’re very much lacking in proper communication skills and any sort of sympathy. I’ve dealt with them for years and somehow came out a lot more… human than they did. I can only hope they’re not calling every police officer dimwitted and arrogantly floating around crime scenes with their noses turned up.” 

“You talk quite bad about them.” 

“They’ve called me worse.”   
The elevator soon opened and the smell of disinfectant hit your nose instantly. It wasn’t anything you’re not used to but it certainly wasn’t a pleasing smell. You followed Spencer through some hallways until coming onto some large glass rooms with autopsy tables, drawers, and evidence laid around. He pushed open a door and a medical examiner dressed in scrubs welcomed him. 

“This is Dr. Y/N Holmes. She’s helping with the case,” Spencer said with a gesture your way. The medical examiner looked you up and down and shook his head. 

“I can’t let unauthorized members look at the bodies,” he said with crossed arms. 

“I am authorized,” you told him. You reached for the badge Mycroft had handed you earlier. 

The doctor laughed. “I’m sure you are, pretty girl, but I need to see some real identification.” 

You took a long stride up to him, nose tilted up. With a hard shove, you handed him the badge. He glanced down, pulled it back from his face, and read it. “If you’d be so kind as to let me pass, I’d greatly appreciate it.” You tore the badge from his hand. “And if you pull something like that again, I will castrate you. With a strand of my hair.” 

The doctor nodded, partly in submission and fear, and began to pull out the victims individually. Spencer had yet to move. 

You put a hand on his elbow, a gentle gesture just to make sure he was okay. He flinched and looked down at your hand that you had now removed. “Are you alright?” 

He nodded quickly. “Yeah,” he answered breathlessly. The place where your fingers had just been burned and he felt his cheeks get hot and they were no doubt red as a tomato. 

“The first two have already been given a proper burial but we have four right now,” the medical examiner said. He started pointing to each of the bodies. “Mack Cullen, Helen Mcnamara, Kristy Ramirez, and Clarke Carpenter. No familial relation-”

“No friendships, disagreements, workplace similarities, mix of races, mix of genders, social class, etc. It’s the same exact M.O. as the one in London. They just happen to be at the wrong place at the wrong time,” you finished. 

“Cullen and Mcnamara both died by asphyxiation, Ramirez by overdose, and Carpenter by blunt force trauma,” Spencer added. 

“Overdose? What did she overdose on?” You asked. 

“Don’t know. She had all the symptoms of an overdose but nothing abnormal showed up on her toxicology report except for blood pressure medication and birth control,” the medical examiner answered. 

“This is the first time he’s used some sort of drug as his weapon,” you thought out loud. And then suddenly it hit you. “He’s using a paralytic drug to subdue his victims before having his way with them. For the first time, he’s messed up and caused an overdose in Ramirez. He’s smart. He has pharmaceutical, medical knowledge. Chemical, too. He knows what’s gonna show up on reports but isn’t trained enough to administer the agent properly. He’s panicking. He knows he messed up.” 

Spencer nodded in recognition. “Possibly dropped out of medical or graduate school? That could be the stressor. Led to his ultimate downfall. Caused a breakdown that eventually became a habit, a lifestyle.” 

A combined lightbulb went off above yourself and Spencer. “Let’s go back up to the BAU,” you said. The doctor started closing the drawers and wished the both of you goodbye. Spencer waved his hand in parting while you gave a slightly less friendly salutations: a middle finger pointed at him as you walked away. 

You found yourself in the elevator once again with Spencer except this time your mind was running. Its gears were turning fast like they always did in the middle of a case. Everything else faded away and you weren’t back to the present until Spencer said loudly, “Y/N!” 

“Huh?” You asked, coming out of your mind. 

“You completely spaced out. Were you okay or is that a normal thing?” He asked.

“Yeah, sorry. Once I start thinking about this stuff, everything else just gets blocked out. Sherlock says he goes to his mind palace. I guess it’s something similar.” 

Spencer nodded. “I get that,” he said. “56% of Americans think best when it’s quiet and there’s little to no distractions. Some thrive in busy and loud situations while others have their best work done alone. It can be linked to the introversion-extroversion spectrum. I’m pretty far on the introvert side and I would assume you are too.” 

“Dr. Reid, I think we’ll get along very well.” 

He smiled and said, “I think so too.”


End file.
